The present invention relates to fluid handling apparatus and in particular, to purge valves for fluid handling apparatus.
Automatic machines have been developed for filling containers with fluids, such as milk and fruit juices. The liquid is supplied from a central reservoir to a dispensing unit. The individual containers or cartons are conveyed under the dispensing unit to receive a predetermined quantity of fluid. Various devices have been proposed for such dispensing units. For examples, U.S. Pat. No. 4,402,461 issued to Mosse, et al. on Sept. 6, 1983, discloses a fluid handling apparatus having an upper bellows for receiving fluid from a main supply, a lower bellows for receiving fluid from the upper bellows, and a midsection therebetween. A filling nozzle located below the lower bellows directs the fluid therein into cartons arranged below the lower bellows.
In normal operation, the top of the upper bellows and the bottom of the lower bellows are fixed to a rigid base, and a drive mechanism attaches at the midsection. In the first half of a cycle, the drive mechanism raises the midsection, simultaneously contracting the upper bellows and expanding the lower bellows. While the upper bellows is contracting, liquid present therein is forced through the midsection into the lower bellows, which is expanding to accept the liquid.
The cycle is completed when the driven mechanism lowers the midsection, simultaneously expanding the upper bellows and contracting the lower bellows. As the upper bellows is expanding, liquid is drawn into it from the main supply. Meanwhile, the lower bellows is contracting, forcing the liquid present in it through the nozzle into a carton situated therebelow. This cycle repeats in response to reciprocating movement of the midsection.
If the double bellows fluid handling apparatus is not to be used for an extended period, the liquid contents in both of the bellows is drained. To start the double bellows fluid handling apparatus when both of the bellows are empty, a valve leading to the nozzle at the bottom of the lower bellows is manually closed by an operator. With the valve closed, the bellows are cycled repeatedly to draw liquid from the upper bellows through the midsection into the lower bellows until a sufficient level of fluid accumulates in the lower bellows.
In the patented apparatus described above, a non-return inlet valve interconnects the upper and lower bellows and allows the liquid to pass from the upper bellows into the lower bellows. In response to an increase in the fluid pressure in the upper bellows, the inlet valve opens against the restraining force of a spring.
A problem with the prior art apparatus is that when the valve interconnecting the lower bellows and the nozzle is closed, the air in the lower bellows cannot easily escape to make room for the incoming liquid. This air is not easily released through the valve interconnecting the upper and lower bellows because of the liquid flowing from the upper bellows into the lower bellows. Thus, the priming of the system, i.e., the initial filling of the lower bellows, is impeded by the resistance the escaping air encounters.